A '''spiral galaxy''' is a [[galaxy]] consisting of a rotating disk of [[star]]s, [[gas]] and [[dust]] which has a number of arms extending outwards from the galactic centre. Some spiral galaxies have a prominent bulge around the centre, while others have a bar crossing the centre with the spiral arms extending from the ends of the bar. | A '''spiral galaxy''' is a [[galaxy]] consisting of a rotating disk of [[star]]s, [[gas]] and [[dust]] which has a number of arms extending outwards from the galactic centre. Some spiral galaxies have a prominent bulge around the centre, while others have a bar crossing the centre with the spiral arms extending from the ends of the bar. |